Electronic governor for fuel-injection type internal combustion engines

ABSTRACT

An electronic governor for fuel-injection type internal combustion engines in which an output voltage inversely proportional to a rotation speed of engine and an output voltage of a blocking oscillator correlated to a position of an accelerator lever of the engine are applied to a differential amplifying circuit whose output is connected to an electromagnetic fuel control mechanism actuating a fuel regulating rod.

United States Patent Tada et a1.

[54] ELECTRONIC GOVERNOR FOR FUEL- INJECTION TYPE INTERNAL COMBUSTIONENGINES [72] Inventors: Yoshiharu Tada; Minoru Sawada,

both of l-ligashi-Matsuyama, Japan [73] Assignee: Diesel Kiki KabushikiKaisha,

Tokyo, Japan 22 Filed: Aug. 5, 1970 [21] Appl.No.: 61,087

[30] Foreign Application Priority Data Sept. 4, 1969 Japan ..44/83640[52] US. Cl. ..l23/102, 123/139 E [51] Int. Cl ..F02m 51/00 [58] Fieldof Search ..l23/97, 102, 118, 32 EA [56] References Cited UNITED STATESPATENTS 3,575,256 4/1971 Jania et a1 ..l23/l02 51 Oct. 3, 1972 3,153,74610/1964 Atkinson ..l23/102 X 3,407,793 10/1968 Lang 1 23/102 3,425,4012/1969 Lang 123/102 3,525,017 8/1970 Rosenberg et a1. ....123/l02 XPrimary Examiner-Laurence M. Goodridge Attorney-Larson, Taylor and Hinds5 7 ABSTRACT An electronic governor for fuel-injection type internalcombustion engines in which an output voltage inversely proportional toa rotation speed of engine and an output voltage of a blockingoscillator correlated to a position of an accelerator lever of theengine are applied to a differential amplifying circuit whose output isconnected to an electromagnetic fuel control mechanism actuating a fuelregulating rod.

lClaim, 2 Drawing Figures ELECTRONIC GOVERNOR FOR FUEL-INJECTION TYPEINTERNAL COMBUSTION ENGINES This invention relates to an electronicgovernor for fuel-infection type internal combustion engines.

In conventional electronic circuits for governors of this type, theoutput signal of a fixed-frequency oscillator is applied to an AC bridgecircuit comprising resistors, inductance and variable inductance whosevalue varies with the position of an accelerator lever of engine, sothat an AC output voltage of the bridge is of a fixed-frequency with itspeak value being determined by the variable inductance valuecorresponding to the position of the accelerator lever, and a DC voltageis produced by integrating this AC output voltage of the bridge. The DCvoltage is then compared against another DC voltage proportional to therotation speed of the engine, and an electromagnetic mechanism forcontrolling a fuel regulating rod, by which the fuel injection quantitydelivered by a fuel injection pump is increased or decreased, isoperated according to the magnitude of the difference between said twoDC voltages. The oscillator in such a circuit is .a main circuitcomponent and may take any of many known forms. But, no matter what formthe oscillator may take, it is not free from the effects of changes inambient temperature and its frequency. changes more or less when atemperature'change occurs. Moreover, conventional electronic circuitsuse an AC bridge circuit, whose resistance and inductance elements varytheir values for an ambient temperature variation occurring between thecold state of the engine at the time of starting and the hot state ofthe engine in normal operation, and also between seasons of the year.When resistance or inductance value changes even slightly, the outputvoltage of the bridge changes widely. These are the drawbacks of theconventional circuits hitherto'used for electronic governors.

The object of this invention is to provide an electronic governorcircuit in which no AC bridge is used and which is designed with the useof a blocking oscillator less subject to the effects of temperaturevariation in order to avoid such drawbacks as are associated withconventional circuits.

Theinvention will be made clear by the following description of anembodiment thereof in reference to the accompanying drawings in which:

FIG. 1 shows an embodiment of an electronic circuit for the governoraccording to the invention; and

F IG. 2 is a graph showing the output characteristics of the electroniccircuit of FIG. 1.

In FIG. 1, a rotation speed detector is shown at 1. This detector iscoupled to a rotating shaft of the fuel injection pump and detects therotation speed electromagnetically. Such devices are, of course,conventional and produce an output voltage corresponding to therotational speed of the shaft of the fuel injection pump. A variableinductance, associated in such a way with the accelerator lever of theengine as to vary its inductance value according to the position of thislever, is designated at 2. As the accelerator lever is moved in thedirection for increasing injection quantity, the core within theinductance 2 moves outwardly to vary the inductance value of the coil.At 3 is shown a movable coil of a control mechanism which moves theregulating rod of the fuel injection pump in response to the outputcurrent of the electronic circuit. A negative conductor is shown at 4.This conductor is connected to the negative side of a battery, notshown, of the engine. A positive conductor is shown at 5. This conductoris connected to the positive side of the same battery. Transistors aredesignated at T, through T diodes at D, through D.,; capacitors at C,through C and resistors at R, through R Referring to the same FIG. 1,the signal produced by the rotation speed detector and corresponding tothe rotation speed of the fuel injection pump is amplified by anamplifying circuit A comprising transistor.T,, resistors R,, R and R andcapacitor C, and C and the output signal of the amplifier A is thendifferentiated and changed to a trigger pulse by a differentiatingcircuit B of known type having capacitor C, and resistor R The triggerpulse is applied through diode D, to a monostable multivibrator C ofknown type having transistors T T T and T ,v diode D capacitor C andresistors R through R,,,. The diode D, eliminates positive pulses fromthe passing signal so that only negative pulses enter the monostablemultivibrator C. This multivibrator supplies its output voltage from thecollector side of its transistor T to an integrating circuit D of knowntype having resistor R,, and capacitor C by which the multivibratoroutput signal is converted to a DC- voltage V,,, whose value isdetermined by following formula: I

V,,V(lkt,N) l where t, is the pulse width determined by the timeconstant of capacitor C, and resistor R in the monostable multivibratorC, V isthe peak value of multivibrator output signal, N is the rotationspeed of the fuel injection pump (that is, of the engine), and k is aconstant. The formula 1 above tells that, if the rotation speed Nincreases, the 'value of V decreases. This voltage V, is applied to thebase of transistor T in a differential amplifier circuit E (which may bea voltage comparator circuit) having transistors T, and T,,, andresistors R and R,,.,.

A blocking oscillator F of known type composed of transistor T capacitorC diode D resistors R, through R, and variable inductance 2 oscillatesat frequency corresponding to the various values of variable inductance2. The output signal of this oscillator F is fed to an amplifyingcircuit C having transistor T,,, capacitor C and resistors R through Rand is by this amplifier G converted to a square waveform, which is thenled to a monostable multivibrator H of known type composed of transistorT diode D capacitor C, and resistors R through R The output signal ofthis multivibrator H is a square waveform signal with a constant pulsewidth and is applied to an integrating circuit l of known type havingresistor R and capacitor C,,. By integration, the square waveform signalwith a constant pulse width is converted to a DC voltage V,,, whosevalue is given by following formula:

V V I2 'f 2 where t, is the pulse width determined by the time constantof capacitor C and resistor R23, V is the peak value of multivibratoroutput signal, and f is-the oscillating frequency of oscillator F. TheDC voltage V,, is applied to the base of transistor T,,, in thedifferential amplifier E mentioned above.

Thus, the degree of the conduction of transistor T in the differentialamplifier circuit E varies according to the difference between these twovoltages V,, and V which may be expressed by equations l and 2 above.Stated specifically, the greater the difference V .V,,, the moreconductive becomes transistor T as the difference diminishes, transistorT. becomes less-conductive; and when V is equal to V transistor '1,becomes non-conductive. The output of this transistor T is amplified atan amplifying circuit J comprising the transistor T and resistor R Theoutput of the circuit .1 is connected to a power amplifying circuit Kcomprising the transistor T and the movable coil 3. Current i that flowsin movable coil 3 varies in response to the rotation speed N of theengine and also to the value of variable inductance 2 which may beindicated, for instance, as L L L (L L In the graph of FIG. 2, thesevalues of inductance are shown as parameters on characteristic curvesrepresenting current 1, taken on the vertical axis, engine rotationspeed N, taken on the horizontal axis. Inductance L varies with theposition of said accelerator lever. Current i indicated in FIG. 2, isequal to the value given by dividing the maximum voltage applying to themovable coil 3 by the internal resistance thereof. This coil may beplaced within a magnetic field of a magnetic-pole cylinder in a knownmanner and subjected to electromagnetic force whose direction isgoverned by F lemings left-hand rule. The force acting on the coil istransmitted through a linkage to the regulating rod of the fuelinjection pump not shown, which, by moving, increases or decreases thefuel injection quantity delivered by the injection pump. It followstherefore that the current i determines the position of the fuelregulating rod for the maximum fuel injection quantity.

The foregoing electronic circuit preforms the speed governing action inthe following manner: Assuming that the fuel regulating rod is soarranged that it will move against the force of a spring in thedirection for increasing injection quantity when a current flowingthrough the movable coil 3 increases, and if the load being carried bythe engine decreases. This load reduction raises engine speed to lowerthe output voltage V of integrating circuit D, thereby decreasing theoutput voltage of power amplifying circuit K and reducing the magnitudeof electromagnetic force acting on coil 3. By this reduction of force oncoil 3, the spring-urged regulating rod shifts in the direction fordecreasing injection quantity. If the rotation speed of the engine slowsdown, the force acting on the movable coil 3 increases to 'move theregulating rod against the force of its spring in the direction forincreasing fuel injection quantity.

Moving the accelerator lever, on the other hand, in order to increasethe fuel injection quantity will lower the oscillating frequency ofblocking oscillator F, so that the output voltage V,, of integratingcircuit I falls to raise the output voltage of differential amplifyingcircuit E, thereby raising the output voltage of power amplifyingcircuit K. This raised output voltage causes the coil 3 to move theregulating rod in the direction for increasing the quantity of fuelinjected. Moving the accelerator lever back to its original positionreverses the above series of events to allow the regulating rod to beforced back b its urging spring in the direction for decreasing fue inection quantity. For each of different positions thatthe acceleratorlever can be moved to take, the governor action described in thepreceding paragraph takes place, for a change in engine load, to varythe coil current i, as illustrated in FIG. 2.

It will be seen from'the foregoing description that the advantages of anelectronic circuit accordingto this invention lies in its simpleconstruction due to a minimum number of circuit elements required andalso in a stable governor action due to the use of a blockingoscillator, which is little affected by changes in ambient temperatureand provides a stable frequency of oscillation.

While the invention has been described in detail with respect toembodiment of the invention it will be understood that various changesand modifications may be made without departing from the spirit andscope of the invention, and it is intended, therefore, to cover all suchchanges and modifications in the appended claim.

-What is claimed is:

I. An electronic governor for a fuel-injection internal combustionengine comprising: means for producing an electrical output signal inaccordance with the rotational speed of the engine fuel pump; amplifiermeans for amplifying said signal; differentiator circuit means connectedto the output of said amplifier means for differentiating the amplifiedsignal; detector means connected to.the output of said differentiatormeans; first monostable multivibrator means connected to the output ofsaid detector means; first integrator circuit means for integrating theoutput signal produced by said first monostable multivibrator means;blocking oscillator means, including a variable impedance means theimpedance value of which is a function of the position of the engineaccelerator operating lever, for producing an output signal having afrequency which is a function of the position of said operating lever;second amplifier means for amplifying the output of said blockingoscillator means; second monostable multivibrator means connected to theoutput of said second amplifier means; second integrator circuit meansfor integrating the output signal produced by said second monostablemultivibrator means; differential amplifier means having a first inputconnected to the output of said first integrator circuit means and asecond input connected to the output of said second integrator circuitmeans; further amplifier means con nected to the output of said.differential amplifier means; power amplifier means connected to theoutput of said further amplifier means; and electromagnetic controlmeans connected to the output of said power amplifier means forcontrolling actuation of a fuel regulating control rod.

1. An electronic governor for a fuel-injection internal combustionengine comprising: means for producing an electrical output signal inaccordance with the rotational speed of the engine fuel pump; amplifiermeans for amplifying said signal; differentiator circuit means connectedto the output of said amplifier means for differentiating the amplifiedsignal; detector means connected to the output of said differentiatormeans; first monostable multivibrator means connected to the output ofsaid detector means; first integrator circuit means for integrating theoutput signal produced by said first monostable multivibrator means;blocking oscillator means, including a variable impedance means theimpedance value of which is a function of the position of the engineaccelerator operating lever, for producing an output signal having afrequency which is a function of the position of said operating lever;second amplifier means for amplifying the output of said blockingoscillator means; second monostable multivibrator means connected to theoutput of said second amplifier means; second integrator circuit meansfor integrating the output signal produced by said second monostablemultivibrator means; differential amplifier means having a first inputconnected to the output of said first integrator circuit means and asecond input connected to the output of said second integrator circuitmeans; further amplifier means connected to the output of saiddifferential amplifier means; power amplifier means connected to theoutput of said further amplifier means; and electromagnetic controlmeans connected to the output of said power amplifier means forcontrolling actuation of a fuel regulating control rod.